1. Field of Invention
This invention relates to a variable power optical system in which aberrations are corrected well while the value of the total length of the optical system relative to image height is being made to become small, and to an image pickup apparatus having the same.
2. Description of the Related Art
Digital cameras, which are provided with a solid-state imaging sensor like CCD (Charge Coupled Device) or CMOS (Complementary Metal-Oxide Semiconductor), have become mainstream instead of film-based cameras in recent years. These digital cameras include various kinds of digital cameras which range from high performance-type digital camera for business to compact popular-type digital camera.
And, in such digital cameras, compact popular-type digital cameras have improved in downsizing because of desires that users easily enjoy photography, so that digital cameras which can be put well in pockets of clothes or bags and are convenient to be carried have appeared. Accordingly, it has become necessary to downsize variable power optical systems for such digital cameras yet more. However, it has been required that variable power optical systems for such digital cameras have not only a small size but also high optical performance (aberrations are corrected well in such variable power optical systems).
Variable power optical systems which meet such requirements include variable power optical systems which are disclosed in International Publication WO 2006/115107 and Japanese Patent Kokai No. 2008-233611 respectively. International Publication WO 2006/115107 relates to a variable power optical system for correcting chromatic aberration of magnification. When an attempt to achieve a super-small-sized variable power optical system is made, the refractive power of a second lens group becomes strong, so that chromatic aberration of magnification at the telephoto end position becomes a problem. In International Publication WO 2006/115107, this problem is corrected by making the Abbe's number of a fourth lens group proper. Japanese Patent Kokai No. 2008-233611 relates to a variable power optical system which has high performances and is downsized and the first lens group of which consists of two lens.